Linking my Stamina bar to sprint

Early on i would like to point out I use C#. Ok So the problem im having is making a sort of sprint ability (using the left shift) that then will let the player sprint at a accelerated speed while it draws energy from a energy GUI. I have the GUI’s script however I have not been able to create a working sprint within it or in another script. So below is a script for my GUI.

    using UnityEngine;
    using System.Collections;
    
    public class EnergyScript : MonoBehaviour {
    	
    		// Stamina Bar
    	public int Maxenergy = 100;
        public int curEnergy = 100;
    	public Texture2D bgImage; 
        public Texture2D fgImage; 
     	public float EnergyBarLength;
    	
    	void Start () {   
    		EnergyBarLength = Screen.width /2;    
    		
    		
    		}
    	
    
    void Update () {
           AddjustcurrentEnergy(0);
    }
    				
    void OnGUI() {
    		
    				
    	 GUI.BeginGroup (new Rect (10,10, EnergyBarLength,20));
           
           GUI.Box (new Rect (10,10, EnergyBarLength,20), bgImage);
     
           GUI.BeginGroup (new Rect (10,10, curEnergy / Maxenergy * EnergyBarLength, 20));
     
        
           GUI.Box (new Rect (10,10,EnergyBarLength,20), fgImage);
    
           
           GUI.EndGroup ();
     
            GUI.EndGroup ();
         }
    void AddjustcurrentEnergy(int adj){
     
        curEnergy += adj;
     
           if(curEnergy <0)
             curEnergy = 0;
     
           if(curEnergy > Maxenergy)
             curEnergy = Maxenergy;
     		if (curEnergy < 100) 
    
           if(Maxenergy <1)
             Maxenergy = 1;
    		
    		EnergyBarLength =(Screen.width /2) * (curEnergy / (float)Maxenergy);
    }
    }

Any help is appreciated.

@Danmietz, I think those lines are just to prevent a possible divide by zero error.

void AddjustcurrentEnergy(int adj){
 
curEnergy += adj;
 
if(curEnergy <0)
curEnergy = 0;
 
if(curEnergy > Maxenergy)
curEnergy = Maxenergy;

if(Maxenergy <1)
Maxenergy = 1;
 
EnergyBarLength =(Screen.width /2) * (curEnergy / (float)Maxenergy);

PS - The “Addjust…” bit irks me I know it’s trival but would you rename it to Adjust…"